Method and equipment for channel sensing and signal transmission

ABSTRACT

A method for channel sensing and signal transmission is provided. The method includes that a signal transmission mode of a communication node in a predefined time window is different from a signal transmission mode of the communication node outside the predefined time window, which includes at least one of a channel sensing mode and a data transmission mode. By performing the method, a frequency domain multiplexing coefficient among nodes adopting the same access technology can be improved, and the coexistence of the access technology and others can be ensured.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/204,283, filed on Jul. 7, 2016, which has issued as U.S. Pat. No.10,873,972 on Dec. 22, 2020 and is based on and claims priority under 35U.S.C. § 119(a) of a Chinese patent application filed on Jul. 16, 2015in the Chinese Patent Office and assigned Serial number 201510419423.1,the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to mobile communication technologies.

Particularly, the present disclosure relates to a method and equipmentfor channel sensing and signal transmission. More particularly, thepresent disclosure relates to a method and base station for channelsensing and signal transmission, and user equipment (UE) for receivingsignals on a carrier in an unlicensed frequency band.

BACKGROUND

The contradiction between the demands of users for high bandwidth radioservices and the lack of frequency resources are becoming increasinglyacute, and thus mobile operators consider using unlicensed frequencybands as the supplement of licensed frequency bands. Accordingly, thedeployment of long term evolution (LTE) in the unlicensed frequencybands is researched initially. The 3rd generation partnership project(3GPP) has begun to researched, under a premise of ensuring that othernodes in unlicensed frequency bands are not impacted, how the spectrumefficiency of whole network is improved through effective carrieraggregation of unlicensed frequency bands and licensed frequency bands.

Usually, an unlicensed frequency band has been assigned for a certainpurpose, for example, radar or WiFi of 802.11. Accordingly, interferencewith the unlicensed frequency band is uncertain, which results in thatthe quality of service (QoS) of LTE transmission is difficult to beensured. However, the unlicensed frequency band may still be used tolow-QoS data transmission. Herein, a LTE system deployed in theunlicensed frequency band is called a licensed-assisted access (LAA)system. In the unlicensed frequency band, it is an important problem howthe interference between the LAA system and another radio system such asthe radar or the WiFi is avoided. Clear channel assessment (CCA) is aconflict avoidance mechanism usually used in the unlicensed frequencyband. A mobile station (STA) must detect a radio channel before sendingsignals. The STA cannot occupy the radio channel to send signals unlessthe STA detects that the radio channel is idle. The LAA system needs tofollow a similar mechanism, so as to ensure a small interference withother signals. A simple mechanism includes that a LAA device (a basestation or user equipment (UE)) is opened or closed dynamicallyaccording to a CCA result. That is, the LAA device sends signals whendetecting that the radio channel is idle, and does not send signals whendetecting that the radio channel is busy. This mechanism is calledlisten before talk (LBT).

In a LTE system, channel measurement is very important. For example,radio resource management (RRM) measurement includes reference signalreceiving power (RSRP) measurement, reference signal receiving quality(RSRQ) measurement or other measurement reflecting the QoS of carriers,so as to provide reference information for the mobility management ofthe LTE system. In a LTE system of the related art, the RRM measurementis based on cell specific reference signal (CRS), channel stateinformation-RS (CSI-RS) or discovery signal (DRS). With the evolvementof the LTE system, new reservation signals may be used to implement theabove measurement. When the measurement is performed, it is necessaryfor the UE to obtain identification (ID) information of a cell or obtainat least coarse synchronization information. Accordingly, whenperforming the RRM measurement, the UE performs channel measurementbased on primary synchronization signal (PSS)/secondary synchronizationsignal (SSS) or other reference signals containing distinguishable cellinformation, and reference signals that can obtain coarse time/frequencydomain synchronization firstly, and then based on the CRS, or the CSI-RSor other reference signals. These reference signals may also provideother information. For example, fine synchronization, CSI measurementand automatic gain control (AGC) reference adjustment may be performedbased on the DRS, or the CRS or the CSI-RS. Since the functions of thesereference signals are very important for the normal operation ofcommunication system, it is necessary to ensure the normal transmissionof these reference signals when designing the transmission mechanism ofthese reference signals.

In the LAA system, especially in the LAA system based on the LBT, thesereference signals cannot be sent in a fixed period all the time. Forexample, a base station may not pass CCA detection sometimes before DRSmeasurement timing configuration (DMTC), and thus can only discard thetransmission of the DRS in this DMTC. In order to increase theprobability of sending the DRS, the duration of the DRS may beshortened, and candidate locations where the DRS is likely to appear maybe increased in each DMTC. For example, suppose the duration of the DMTCis 6 ms and the duration of the DRS is 1 ms, the candidate locationswhere the DRS is likely to appear may be the i^(th) ms in the DMTC,where i=1, 2, 3, 4, 5, 6. In this case, if the CCA detection performedby the base station before any one of the six candidate locations in theDMTC is passed, the base station may send the DRS on the candidatelocation. In order to ensure the probability of sending the DRS andavoid the impact on other communication systems in the unlicensedfrequency band, the LBT mechanism of the DRS may be different from anormal data transmission mechanism. For example, the DRS may adopt afaster LBT mechanism, by which the DRS may be sent through one CCAdetection. Data signals may adopt a load based equipment (LBE) mechanismsimilar to WiFi. For example, the data signals may not be sent unlessmultiple CCA slots are idle. For the CCA detection adopted when sendingthe DRS, the base station may find, through simple energy detection,that detected energy is larger than a predefined threshold, and thusdetermines that a channel detected in this CCA slot is busy and cannotbe used for sending the DRS. It should be noted that, the detectedenergy may be come from signals of other communication systems such asWiFi, or contain signals of the same communication system, for example,the LAA system. In order to avoid impact among LAA systems, especiallythe impact on the DRS, a new mechanism should be adopted. The newmechanism may be a new transmission mechanism, or a new CCA mechanism.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method for channel sensing and signaltransmission, so as to improve a frequency domain multiplexingcoefficient among nodes adopting the same access technology, and ensurethe coexistence of the access technology and others.

In accordance with an aspect of the present disclosure, a method forchannel sensing and signal transmission on a cell in an unlicensedfrequency band is provided. The method includes performing, by a sendingnode, channel sensing before sending at least one of data signals andreference signals, determining whether to send the at least one of thedata signals and/the reference signals according to a result of thechannel sensing, after the determining of whether to send the at leastone of the data signals and the reference signals and when sending theat least one of the data signals and the reference signals in apredefined time window, not sending, by the sending node, any signal orsending predefined signals on first time-frequency resources, whereinthe first time-frequency resources are at least one of in the timewindow and immediately adjacent to a beginning of the time window.

The predefined time window is a time window of reference signals thatare sent for performing radio resource management (RRM) measurement, ora time window of reference signals that are sent for performing channelstate information (CSI) measurement, or a time window of referencesignals that are sent for performing synchronization.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and are immediatelyadjacent to the beginning of the time window.

In a time dimension, each first time-frequency resources occupy Xorthogonal frequency division multiplexing (OFDM) symbols, and infrequency dimension, each first time-frequency resources contain allsub-carriers, all sub-carriers in a system bandwidth, or allsub-carriers in a predefined bandwidth.

The sending node does not send any signal on the first time-frequencyresources, wherein X is a positive real number.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and are immediatelyadjacent to the beginning of the time window.

In a time dimension, each first time-frequency resources occupy X OFDMsymbols, and in frequency dimension, each first time-frequency resourcescontain part of sub-carriers in a system bandwidth or a predefinedbandwidth.

The sending node does not send any signal on the first time-frequencyresources, wherein X is a positive real number.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and are immediatelyadjacent to the beginning of the time window.

In a time dimension, each first time-frequency resources occupy X OFDMsymbols, and in a frequency dimension, each first time-frequencyresources contain all or part of sub-carriers in a system bandwidth or apredefined bandwidth.

The sending node sends predefined signals on the first time-frequencyresources, wherein X is a positive real number.

The time window is a discovery signal (DRS) measurement timingconfiguration (DMTC) window, and the first time-frequency resources areat least one of X OFDM symbols at the beginning or end of a possiblelocation of a DRS that appears in the DMTC time window periodically, andlocated prior to the beginning of the first possible location of the DRSthat is immediately adjacent to the beginning of the DMTC time window.

If the sending node sends the data signals and the reference signals inthe time window or sends the data signals in the time window, a processthat the sending node does not send any signal on the firsttime-frequency resources includes avoiding, by the sending node, mappingthe sent data signals and reference signals or the sent data signals tothe first time-frequency resources through rate matching or puncturing.

The first time-frequency resources are located in the DMTC time windowand are not prior to the beginning of resources for sending the DRS bythe sending node.

If the first time-frequency resources are located at the end of asubframe, the last subframe in the DMTC time window does not contain thefirst time-frequency resources.

If the first time-frequency resources and the location of a referencesignal of the related art overlap, the reference signal of the relatedart is sent on other resources other than the first time-frequencyresources.

If only the reference signals are sent in the time window and thereference signals are reference signals in the DRS, all or part ofresources located between the last OFDM symbol of the last possiblelocation of the DRS and the first OFDM symbol of the next possiblelocation of the DRS are the first time-frequency resources.

A method for sending the reference signals includes the following.

Sending the reference signals in the DRS on the location of resources ofthe related art, wherein the location of the first time-frequencyresources is not filled when padding signals are sent, and if a subframewhere the first time-frequency resources are located supports a sendingmode based on a demodulation reference signal (DM-RS), mapping the DM-RSto the location of resources other than the first time-frequencyresources.

Sending the reference signals in the DRS according to a new mappingmode, and reserving at least X1 OFDM symbols between the last OFDMsymbol of the reference signals in the DRS and the first OFDM symbol atthe next location of the DRS.

When the channel sensing is performed in the time window, the channelsensing includes performing type 2 channel sensing on secondtime-frequency resources in the time window.

The second time-frequency resources are a subset or universal set of thefirst time-frequency resources, or the second time-frequency resourcesand the first time-frequency resources intersect partially.

The second time-frequency resources appear periodically ora-periodically in the time window for many times.

Performing the type 2 channel sensing on the second time-frequencyresources includes the following.

Performing initial clear channel assessment (CCA) detection on eachsecond time-frequency resources, if the initial CCA detection is passed,sending the at least one of the data signals and the reference signalson other resources except the first time-frequency resources until thenext second time-frequency resources, otherwise, not sending the atleast one of the data signals and the reference signals until the nextsecond time-frequency resources.

The second time-frequency resources appear periodically ora-periodically in the time window for many times.

Performing the type 2 channel sensing on the second time-frequencyresources includes the following.

Performing initial CCA detection on each second time-frequencyresources, if the initial CCA detection is passed, sending the at leastone of the data signals and the reference signals on other resourcesexcept the first time-frequency resources until the next secondtime-frequency resources, otherwise, performing enhanced CCA (eCCA)detection, if the eCCA detection is passed before at least one of thebeginning of the next second time-frequency resources and the beginningof predefined partial subframes, sending the at least one of the datasignals and the reference signals on other resources except the firsttime-frequency resources until the next second time-frequency resources,if the eCCA detection is not passed before the beginning of the nextsecond time-frequency resources, not sending the at least one of thedata signals and the reference signals until the next secondtime-frequency resources.

The second time-frequency resources appear periodically ora-periodically in the time window for many times.

Performing the type 2 channel sensing on the second time-frequencyresources includes the following.

Performing initial CCA detection on each second time-frequencyresources, if the initial CCA detection is passed, sending the at leastone of the data signals and the reference signals on other resourcesexcept the first time-frequency resources until the next secondtime-frequency resources, otherwise, performing eCCA detection, if theeCCA detection is passed before the beginning of the next secondtime-frequency resources, sending the at least one of the data signalsand the reference signals on other resources except the firsttime-frequency resources until the next second time-frequency resources,and performing the initial CCA detection, if the eCCA detection is notpassed before the beginning of the next second time-frequency resources,not sending the at least one of the data signals and the referencesignals until the next second time-frequency resources, and continuingthe eCCA detection.

The second time-frequency resources appear periodically ora-periodically in the time window for many times.

Performing the type 2 channel sensing on the second time-frequencyresources includes the following.

When the sending node is in an idle state, performing initial CCAdetection on current second time-frequency resources, if the initial CCAdetection is passed, sending the at least one of the data signals andthe reference signals on other resources except the first time-frequencyresources until the next second time-frequency resources, and performingthe initial CCA detection, otherwise, performing eCCA detection, if theeCCA detection is passed before the beginning of the next secondtime-frequency resources, sending the at least one of the data signalsand the reference signals on other resources except the firsttime-frequency resources until the next second time-frequency resources,and performing the initial CCA detection, if the eCCA detection is notpassed before the beginning of the next second time-frequency resources,not sending the at least one of the data signals and the referencesignals until the next second time-frequency resources, continuing theeCCA detection or performing the eCCA detection again.

When the sending node is not in an idle state, performing eCCA detectionon each second time-frequency resources, if the eCCA detection ispassed, sending the at least one of the data signals and the referencesignals on other resources except the first time-frequency resourcesuntil the next second time-frequency resources, and performing the eCCAdetection again, otherwise, not sending the at least one of the datasignals and the reference signals until the next second time-frequencyresources, and continuing the eCCA detection or performing the eCCAdetection again.

The second time-frequency resources appear periodically ora-periodically in the time window for many times, and signals aredirectly sent on other resources except the first time-frequencyresources without performing initial CCA detection on the secondtime-frequency resources.

The eCCA detection is performed by adopting zero defer, or adopting adefer shorter than or equal to slot length of channel sensing performedoutside the time window.

The length of an initial CCA detection slot in the type 2 channelsensing is larger than, smaller than or equal to the length of aninitial CCA detection slot in the type 2 channel sensing performedoutside the time window.

Data transmission before the last first time-frequency resources in thetime window is determined whether to be performed according to a channelsensing result of the type 2 channel sensing.

The type 2 channel sensing is performed when there is data to be sent inthe time window.

In a scenario that a channel has been occupied before the time windowthrough channel sensing to send signals, performing the type 2 channelsensing in the time window, if the channel has not been occupied beforethe time window through channel sensing and the sending node has data tobe sent but has no DRS to be sent, performing the type 1 channel sensingin the time window, or performing the type 2 channel sensing in the timewindow.

In a scenario that the channel has been occupied before the time windowthrough channel sensing, a scenario that the channel has not beenoccupied before the time window through channel sensing, and a scenariothat the duration of occupying the channel through the type 2 channelsensing exceeds a defined threshold, modes for performing the type 2channel sensing in the time windows are the same or different.

When data is not sent but the DRS is sent and the channel sensing isperformed in the time window, the channel sensing includes thefollowing.

Performing, by the sending node, type 3 channel sensing on thirdtime-frequency resources, and determining whether to send the DRS in thetime window according to a channel sensing result, the thirdtime-frequency resources and the first time-frequency resources overlap,and the type 3 channel sensing is energy detection or sequence detectionin time domain or in frequency domain.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and immediatelyadjacent to the beginning of the time window.

On time dimension, each first time-frequency resources occupy X OFDMsymbols, and on frequency dimension, each first time-frequency resourcescontain all sub-carriers, or all sub-carriers in a system bandwidth orall sub-carriers in a predefined bandwidth.

The sending node does not send any signal on the first time-frequencyresources, wherein X is a positive real number.

The channel sensing performed by the sending node on the thirdtime-frequency resources is the energy detection in time domain.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and immediatelyadjacent to the beginning of the time window.

In a time dimension, each first time-frequency resources occupy X OFDMsymbols, and in a frequency dimension, each first time-frequencyresources contain part of sub-carriers in a system bandwidth or apredefined bandwidth.

The sending node does not send any signal on the first time-frequencyresources, wherein X is a positive real number.

The channel sensing performed by the sending node on the thirdtime-frequency resources is the energy detection in frequency domain.

The first time-frequency resources appear at least one of periodicallyor a-periodically in the time window for many times, and immediatelyadjacent to the beginning of the time window.

In a time dimension, each first time-frequency resources occupy X OFDMsymbols, and in a frequency dimension, each first time-frequencyresources contain all or part of sub-carriers in a system bandwidth or apredefined bandwidth.

The sending node sends predefined signals on the first time-frequencyresources, wherein X is a positive real number.

The channel sensing performed by the sending node on the thirdtime-frequency resources is the sequence detection in time domain or infrequency domain.

The third time-frequency resources appear periodically in the timewindow.

After performing the type 3 channel sensing every time, if the type 3channel sensing is passed, the sending node sends the DRS at the closestsending location of the DRS, otherwise, when there is no data to besent, performing the type 3 channel sensing on the next thirdtime-frequency resources.

If the type 3 channel sensing is passed on the first time-frequencyresources, the sending node does not send signals or sends predefinedsignals on the first time-frequency resources until the closest sendinglocation of the DRS, and sends the DRS, or the sending node sendsreservation signals on the first time-frequency resources until theclosest sending location of the DRS, and sends the DRS.

An equipment for channel sensing and signal transmission on a cell in anunlicensed frequency band includes a channel sensing unit and a signalsending unit.

The channel sensing unit is configured to perform channel sensing beforesending at least one of data signals and reference signals, anddetermine whether to send the at least one of the data signals and thereference signals according to a channel sensing result.

The signal sending unit is configured to send signals when the channelsensing unit determines to send at least one of the data signals and thereference signals, and when sending the at least one of the data signalsand the reference signals in a predefined time window, not to sendsignals or send predefined signals on first time-frequency resources.

The first time-frequency resources being in at least one of the timewindow and immediately adjacent to the beginning of the time window.

As can be seen from the above solution of the present disclosure,because signals are not sent or only predefined signals are sent on somereserved resources, channel sensing resources for sending referencesignals may be reserved for other sending nodes, thereby avoiding that abase stations of the licensed-assisted access (LAA) system hindersanother base station from using the unlicensed frequency band, improvingthe frequency domain multiplexing coefficient among nodes adopting thesame access technology, and ensuring the coexistence of the accesstechnology and others.

Further, through setting the type 2 channel sensing on the secondtime-frequency resources, the length of listen before talk (LBT) may beshortened when the data signals and the reference signals are sent,thereby rapidly sending the reference signals. In addition, throughsetting the type 3 channel sensing on the third time-frequencyresources, the impact among the channel sensing of different basestations of the LAA system can be avoided.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a flowchart illustrating a method for channel sensing andsignal transmission according to a first embodiment of the presentdisclosure;

FIGS. 2A and 2B are diagrams illustrating first time-frequency resourcesaccording to various embodiments of the present disclosure;

FIGS. 3A, 3B, and 3C are diagrams illustrating data signals and firsttime-frequency resources when the data signals have been sent before adiscovery signal (DRS) measurement timing configuration (DMTC) timewindow according to various embodiments of the present disclosure;

FIGS. 4A, 4B, and 4C are diagrams illustrating first time-frequencyresources only located in a DMTC time window according to variousembodiments of the present disclosure;

FIG. 5 is a diagram illustrating first time-frequency resources and DRSduration that has been shortened to 12 orthogonal frequency divisionmultiplexing (OFDM) signals according to an embodiment of the presentdisclosure;

FIG. 6 is a diagram illustrating mapping of demodulation referencesignal (DM-RS) according to an embodiment of the present disclosure;

FIG. 7 is a diagram illustrating resource mapping when the density of RSis increased according to an embodiment of the present disclosure;

FIG. 8 is a diagram illustrating first time-frequency resources and aDRS in which reference signals adopts a new mapping mode according to anembodiment of the present disclosure;

FIGS. 9A and 9B are diagrams illustrating first time-frequency resourceswhen only reference signals are sent and first time-frequency resourceswhen data signals/both data signals and reference signals are sentaccording to various embodiments of the present disclosure;

FIG. 10 is a diagram illustrating first time-frequency resourcesadopting a second definition mode according to an embodiment of thepresent disclosure;

FIG. 11 is a diagram illustrating first time-frequency resourcesadopting a third definition mode according to an embodiment of thepresent disclosure;

FIG. 12 is a diagram illustrating a first implementation mode of type 2channel sensing according to an embodiment of the present disclosure;

FIG. 13 is a diagram illustrating a second implementation mode of type 2channel sensing according to an embodiment of the present disclosure;

FIG. 14 is a diagram illustrating a third implementation mode of type 2channel sensing according to an embodiment of the present disclosure;

FIG. 15 is a diagram illustrating type 2 channel sensing in a scenariothat there are data signals to be sent in a DMTC time window accordingto an embodiment of the present disclosure;

FIG. 16 is a diagram illustrating type 2 channel sensing in a scenariothat a channel has been occupied before a DMTC time window to send datasignals according to an embodiment of the present disclosure;

FIG. 17 is a diagram illustrating type 2 channel sensing performed in aDMTC time window through two modes according to an embodiment of thepresent disclosure;

FIG. 18 is a flowchart illustrating a method for channel sensing andsignal transmission according to a second embodiment of the presentdisclosure;

FIG. 19 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources are a universal set of first time-frequencyresources according to an embodiment of the present disclosure;

FIG. 20 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources is a superset of first time-frequency resourcesaccording to an embodiment of the present disclosure; and

FIG. 21 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources and first time-frequency resources intersectpartially according to an embodiment of the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Considering the problems mentioned in the background, the presentdisclosure provides a new method for channel sensing and signaltransmission. Through proper signal transmission and/or enhanced clearchannel assessment (CCA) procedure, reference signals can be senteffectively in limited resources, and it can be avoided that datasignals being sent impact the reference signals to be transmitted, or itcan be avoided that reference signals being sent impact the referencesignals to be transmitted. In the present disclosure, it is determinedthrough channel sensing whether data signals and/or reference signalsare to be sent. After determining that the data signals and/or thereference signal are to be sent, a sending node reserves time-frequencyresources when sending signals in a time window in which the referencesignals are sent. These reserved time-frequency resources are not usedfor sending data signals and/or reference signals of a cell, but areused for performing channel sensing for reference signals such as adiscovery signal (DRS) by other nodes. Accordingly, it can be avoidedthat a base stations of the licensed-assisted access (LAA) systemhinders another base station from using an unlicensed frequency band.The reserved time-frequency resources are called first time-frequencyresources. Further, if the CCA detection of the cell is performed beforethe data signals and/or the reference signals are sent in the timewindow in which the reference signals are sent, the CCA detection of thecell may be performed outside the time window or in the time window. TheCCA detection of the cell performed in the time window may be performedon second time-frequency resources, or may be performed on thirdtime-frequency resources when only the reference signals are sent butthe data are not sent, e.g., the transmission including the DRS but notincluding a physical downlink shared channel (PDSCH). Theimplementations of the present disclosure will be illustratedhereinafter with reference to embodiments.

A first embodiment is implemented as follows.

The first embodiment describes signal processing on the firsttime-frequency resources and channel sensing processing on the secondtime-frequency resources.

FIG. 1 is a flowchart illustrating a method for channel sensing andsignal transmission according to an embodiment of the presentdisclosure.

FIGS. 2A and 2B are diagrams illustrating a method for channel sensingand signal transmission according to the first embodiment of the presentdisclosure.

Referring to FIGS. 2A and 2B, the method includes following blocks.

At block 101, when sending data signals and/or reference signals in apredefined time window, a sending node does not send signals or sendspredefined signals on first time-frequency resources that are in thepredefined time window and/or immediately adjacent to the beginning ofthe time window.

At actual applications, before sending the data signals and/or thereference signals, channel sensing should be performed firstly, and thenit is determined according to a channel sensing result whether the datasignals and/or the reference signals are to be sent. For consecutivesubframes of the data signals and/or the reference signals performed inthe time window, the channel sensing may occur before the time window oroccur in the time window. The new channel sensing method provided by thepresent disclosure is mainly used for the channel sensing in the timewindow or just right before the time window, for example, block 102 ofthe first embodiment. The channel sensing performed before the timewindow is not described in the first embodiment.

Preferably, the sending node may be a base station or user equipment(UE). Hereinafter, all embodiments are described by taking the basestation as an example.

Preferably, the first time-frequency resources, a receiving node and thesending node are well known. For example, the sending node is a basestation, and the receiving node is UE or another base station.

The data signals may contain PDSCH, physical downlink control channel(PDCCH), enhanced PDCCH (EPDCCH) or other newly defined control signals.The reference signals may be one or more reference signals of therelated art in the long term evolution (LTE) system, or may be othernewly defined reference signals with specific functions.

Preferably, the predefined time window may be a time window of referencesignals sent for performing radio resource management (RRM) measurement,for example, DRS measurement timing configuration (DMTC). As mentionedabove, the reference signals for performing RRM measurement (DRS) mayalso have a cell distinguishing function, may have a function providingcoarse time synchronization and/or fine time synchronization and/orfrequency domain synchronization, may have an automatic gain control(AGC) reference adjustment function and may have a channel stateinformation (CSI) measurement function.

Preferably, the predefined time window is a time window of referencesignals sent for performing CSI measurement.

Preferably, the predefined time window is a time window of referencesignals for performing synchronization.

The time window may appear periodically. For example, the duration ofthe DMTC is called DMTC duration, and the time location of a DMTC timewindow is determined by a DMTC period called DMTC-periodicity and DMTCoffset called DMTC-offset. The following embodiments are described bytaking the DMTC time window as an example. Other time windows aresimilar to the DMTC time window.

The first time-frequency resources may appear in the time windowperiodically or a-periodically for a plurality of times. For example, inthe time window, time resources may be divided into N₁ parts, and eachpart may be divided into M₁ sub-resources. One part of the M₁sub-resources is used to send usable signals, for example, send datasignals, or send data signals and a DRS, or send the DRS, and the otherpart of the M₁ sub-resources are the first time-frequency resources. Itshould be noted that, the N₁ parts may have the same length or havedifferent lengths. Similarly, the M₁ sub-resources may have the samelength or have different lengths. According to the occupation mode ofthe first time-frequency resources on time dimension, the firsttime-frequency resources may appear in the time window for a pluralityof times. The first time-frequency resources may appear periodically(for example, when the N₁ parts have the same length and the M₁sub-resources also have the same length) or appear a-periodically for aplurality of times. The definition and processing for the firsttime-frequency resources may be always the same no matter whether thefirst time-frequency resources appear periodically or a-periodically.The definition of the first time-frequency resources and processing forsignals on the first time-frequency resources will be describedhereinafter by taking an example that the first time-frequency resourcesappear periodically.

The first time-frequency resources may be defined through threedefinition modes.

In a first definition mode, the first time-frequency resources appear ina period T1 in the time window, and/or appear at a location immediatelyadjacent to the beginning of the time window. The first time-frequencyresources occupy X orthogonal frequency division multiplexing (OFDM)symbols on time dimension, where X is an integer (for example, X=1) or afraction. The first time-frequency resources contain all sub-carriers orcontain all sub-carriers in a predefined bandwidth on frequencydimension. On these time-frequency resources, the base station does notsend any signal.

In the first definition mode, preferably, suppose there are multiplepossible locations of the DRS in the DMTC time window and an intervalbetween the beginnings of two possible locations of the DRS is T2, theperiod T1 of the first time-frequency resources is equal to N*T2, whereN is an integer, and the offset of the first time-frequency resourcesrelative to the DRS is A on time dimension. The first time-frequencyresources occupy X OFDM symbols on time dimension, where X is an integer(for example, X=1) or a fraction. Accordingly, the length of timeoccupied by the first time-frequency resources is equal to the length ofM channel sensing slots for sending the DRS, where M is a positiveinteger, for example, M=1.

Referring to FIGS. 2A and 2B, the duration of the DRS is 1 ms, and thelength of the DMTC time window is 6 ms. Suppose the DRS have 6 possiblelocations, where the beginnings of the possible locations i=1, 2, 3, 4,5, 6 ms, i.e., the 1^(th)˜6^(th) ms in the DMTC time window, the periodof the first time-frequency resources is 1 ms. The offset Δ is set tomake the first time-frequency resources be X=1 OFDM symbol at the i^(th)ms beginning or end in the DMTC time window. For simplification, timeand frequency resources are called time-frequency resources for short inthe drawings of the present disclosure. Referring to FIG. 2A, the DMTCtime window is divided into N₁=6 parts of time resources, and the lengthof each part of time resources is 1 ms. Each part of time resources isdivided into M₁=2 parts of sub-resources. One part of sub-resources isused for sending usable signals, for example, sending the DRS, and theother part of sub-resources is the first time-frequency resources. N=1and T1=T2, that is, for each possible DRS transmission, there is thefirst time-frequency resources, and the first time-frequency resourcesare located at the last OFDM symbol of the 1^(th)˜5^(th) sub-frames inthe DMTC time window and at the last OFDM symbol of a sub-frame beforethe beginning of the DMTC time window. Referring to FIG. 2B, the DMTCtime window is divided into N₁=3 parts of time resources, and the lengthof each part of time resources is 2 ms. Each part of time resources aredivided into M₁=2 parts of sub-resources. One part of sub-resources isused for sending usable signals, and the other part of sub-resources isthe first time-frequency resources. N=2 and T1=2T2, that is, for eachtwo possible DRS transmissions, there is the first time-frequencyresources, and the first time-frequency resources are located at thefirst OFDM symbol of the 1^(th), 3^(th) and 5^(th) sub-frames in theDMTC time window. In the first definition mode, an implementation thatsignals are not sent on the first time-frequency resources will bedescribed hereinafter.

FIGS. 3A, 3B, and 3C are diagrams illustrating data signals and firsttime-frequency resources when the data signals have been sent before aDMTC time window according to various embodiments of the presentdisclosure.

(1) If the base station is sending data signals and reference signals oris sending data signals, the base station does not send any signal onthe first time-frequency resources, and may avoid mapping the datasignals and/or reference signals to the first time-frequency resourcesthrough rate matching or puncturing. Referring to FIGS. 3A and 3B, ifthe duration of the DRS is T2=0.5 ms or T2=1 ms and the period of thefirst time-frequency resources is T1=1 ms, the base station excludes thelast OFDM symbol of a subframe immediately adjacent to the beginning ofthe DMTC time window and the last OFDM symbol of 5 subframes in the DMTCtime window when mapping the data signals to physical resources. Afterthe first time-frequency resources, the base station may send the datasignals and/or reference signals again. It should be noted that achannel may be occupied by another communication node. Referring to FIG.3C, after the last OFDM symbol of the first subframe in the DMTC timewindow becomes idle, the channel is occupied by another communicationnode, for example, resources from the second subframe to the lastsubframe in the DMTC time window are all occupied. In this case, if thebase station does not perform listen before talk (LBT) but continuessending the data signals and/or reference signals, collision will occur.If the base station performs LBT, the base station cannot continuesending the data signals and/or reference signals until the channelbecomes idle. How the base station performs LBT will be described atblock 102.

Preferably, in order to avoid that the base station being sending datasignals cannot grab a channel for sending the DRS again in time afterthe first time-frequency resources, the first time-frequency resourcesof the base station do not contain a subframe located before resourcesfor sending the DRS by the base station in the same burst. That is, thefirst time-frequency resources of the base station is in the DMTC timewindow and is not prior to the beginning of the resources for sendingthe DRS by the base station. For example, if the base station sends theDRS in the first subframe in the DMTC time window, the firsttime-frequency resources do not contain the subframe immediatelyadjacent to the beginning of the DMTC time window. That is, the firsttime-frequency resources are only in the DMTC time window, as shown inFIGS. 4A and 4B. FIG. 4C shows an example that the DRS is located in thesecond subframe in the DMTC time window.

FIGS. 4A, 4B, and 4C are diagrams illustrating first time-frequencyresources only located in a DMTC time window according to variousembodiments of the present disclosure.

Preferably, if the first time-frequency resources are located at the endof a subframe, the last subframe in the DMTC time window does notcontain the first time-frequency resources. For example, if there are 6subframes in the DMTC time window, the first time-frequency resourcesare only in the 1^(th)˜5^(th) subframes.

Preferably, if the first time-frequency resources and the location of ademodulation (DM)-reference signal (RS) of the related art overlap, thelocation of the DM-RS needs to be reset, referring to the description at(2) and FIG. 6. Similarly, if the first time-frequency resources and thelocation of another RS of the related art overlap, the location of theRS needs to be reset.

(2) If the base station is sending reference signals but does not senddata signals, especially, if the base station is sending the DRS, forexample the base station transmits a transmission including the DRS butnot including the PDSCH, the base station maps the DRS and other paddingsignals or control signals transmitted together with DRS on theresources, which are not part of the first time-frequency resources.Herein, the transmission of the reference signals is mainly discussed,and for reservation signals that are sent before sending the referencesignals and used for occupying a channel or providing other functions,it may map on the first time-frequency resources or may not. In onecase, the base station has grabbed the channel through CCA detectionbefore the end of the first time-frequency resources. In this case, thebase station may immediately send signals after the base stationfinishes the CCA detection, for example, transmit reservation signals tohold the channel, and begins to send the DRS until the nearest locationfor sending the DRS. In this case, the reservation signals are sent inthe part of the first time-frequency resources. The reservation signalsmay not be distinguished by other base stations. In this way, thereservation signals before the DRS transmitted on the firsttime-frequency resources from the base station A may interfere with theCCA detection performed by the base station B. Because the base stationB is unable to distinguish the base station A, thereby resulting in thatthe base station B deems that the channel is busy when performing CCAdetection. However, an advantage lies in that the priority of the basestation A only sending the DRS can be ensured because the transmissionof the DRS is more important than the transmission of the data signals.In another case, the base station may grab the channel through CCAdetection before the end of first time-frequency resources, but needs towait until the end of the first time-frequency resources when sendingthe reservation signals, or sends signals that can be distinguished byother base stations on corresponding resources, to avoid the impact onother base stations sending data signals.

Specifically, the base station is sending the reference signals, andfollowing implementation modes may be adopted.

FIG. 5 is a diagram illustrating first time-frequency resources and DRSduration that has been shortened to 12 OFDM signals according to anembodiment of the present disclosure.

In an implementation mode, the mapping of reference signals in the DRSsuch as primary synchronization signal (PSS)/secondary synchronizationsignal (SSS)/cell specific reference signal (CRS)/CSI-RS still adoptsthe location of the LTE system of the related art, but the paddingsignals for occupying the channel fill resource location until the lastOFDM symbol where all reference signals of the DRS are located.Accordingly, the duration of the DRS may not be 1 subframe, but isshortened to 12 OFDM symbols, as shown in FIG. 5. The PSS is in the lastOFDM symbol of the 1^(st) slot in the DRS duration, and the SSS is inthe penultimate OFDM symbol of the 1^(st) slot in the DRS duration. TheCRS is in the first and 5^(th) OFDM symbol in both slots in the DRSduration, and the CSI-RS is in the 10^(th) and 11^(th) OFDM symbol inthe DRS duration if the CSI-RS of the DRS is configured. In thisimplementation mode, the first time-frequency resources are all or partof resources between the last symbol of the last possible location ofthe DRS and the first symbol of the next possible location of the DRS,for example, the last two OFDM symbols in the subframe containing theDRS if the DRS duration is only 12 OFDM symbols. If the subframe needsto support a transmission mode based on the DM-RS, the DM-RS may bemapped to other OFDM symbols.

FIG. 6 is a diagram illustrating mapping of DM-RS according to anembodiment of the present disclosure.

Referring to FIG. 6, the DM-RS in the first slot is moved to the thirdOFDM symbol of the first slot and the DM-RS in the second slot is movedto the fourth OFDM symbol of the second slot, which is the same as theDM-RS pattern of the special subframe configurations 3, 4, 8, 9 of therelated art. Of cause, it is feasible that the DM-RS in the second slotis moved to the third and fourth OFDM symbols of the second slot, butthe location of the DM-RS in the first slot is kept unchanged. That is,the DM-RS in the first slot occupies the last two OFDM symbols of thefirst slot in other physical resource blocks (PRBs) which do not containthe PSS/SSS. If the density of partial RSs needs to be increased basedon the DRS of the related art, the OFDM symbols where the increased RSsare located are not posterior to the location of the last OFDM symbolwhere all reference signals of the DRS of the related art are located,as shown in FIG. 7.

FIG. 7 is a diagram illustrating resource mapping when the density of RSis increased according to an embodiment of the present disclosure.

It should be noted that, in the above mentioned drawings, the paddingsignals occupy all time-frequency resources except the reference signalsand the first time-frequency resources. However, for convenience ofdescription, the padding signals may only occupy partial resources onthe frequency domain as long as the prescript of the unlicensedfrequency band is met.

In another implementation mode, if the reference signals in the DRSadopt a new mapping mode, all signals should be centralized as much aspossible when being mapped. All or part of resources from the last OFDMsymbol of the last location of the DRS to the first OFDM symbol of thenext location of the DRS is the first time-frequency resources. On thefirst time-frequency resources, no signal is sent, as shown in FIG. 8.

FIG. 8 is a diagram illustrating first time-frequency resources and aDRS in which reference signals adopts a new mapping mode according to anembodiment of the present disclosure.

It should be noted that, the first time-frequency resources in ascenario that the base station is sending the reference signals and thefirst time-frequency resources in a scenario that the base station issending the data signals/data signals and reference signals aredifferent. For example, suppose the first time-frequency resources onwhich the base station is sending the reference signals are firstresources A and the first time-frequency resources on which the basestation is sending the data signals/data signals and reference signalsare first resources B, the period T1 of the first resources A may be Ntimes the period T2 of the first resources B in the DMTC time window.

FIGS. 9A and 9B are diagrams illustrating first time-frequency resourceswhen only reference signals are sent and first time-frequency resourceswhen data signals/both data signals and reference signals are sentaccording to various embodiments of the present disclosure.

Referring to FIG. 9A, in the DMTC time window, a period of possiblelocations of the DRS is 0.5 ms, so the period T1 of the first resourcesA that are reserved by the base station when sending the DRS is 0.5 ms,and the period T2 of the first resources B that are reserved by the basestation when sending the data signals is 1 ms.

Referring to FIG. 9B, in the DMTC time window, the period of possiblelocations of the DRS is 1 ms, so the period T1 of the first resources Athat are reserved by the base station when sending the DRS is 1 ms, andthe period T2 of the first resources B that are reserved by the basestation when sending the data signals is equal to T1, i.e., 1 ms.However, the first resources B for sending the data signals by the basestation contain resources before the DMTC time window, but the firstresources A for sending the DRS by the base station do not contain theresource before the DMTC time window. In this embodiment, the firsttime-frequency resources for sending the reference signals by the basestation and the first time-frequency resources for sending the datasignals/data signals and reference signals are the same.

In a second definition mode, the first time-frequency resources appearin the period T1 in the time window, and/or appear at a locationimmediately adjacent to the beginning of the time window. The firsttime-frequency resources occupy X OFDM symbols on time dimension, whereX is an integer (for example, X=1) or a fraction. The firsttime-frequency resources occupy a part of sub-carriers on frequencydimension. For example, on frequency dimension, in the entire systembandwidth or in a predefined bandwidth, the first time-frequencyresources occupy a part of sub-carriers in an interval F1, or occupy apart of sub-carriers according to a predefined pattern. On thesesub-carriers, the base station does not send any signal. For example,the first time-frequency resources are the last OFDM symbol in theperiod T1. In the OFDM symbol, F1=2 is an interval. That is, there isone idle sub-carrier every other one sub-carrier, and other sub-carriersmay be used for sending data signals or reservation signals, forexample, referring to the first pattern shown in FIG. 10.

FIG. 10 is a diagram illustrating first time-frequency resourcesadopting a second definition mode according to an embodiment of thepresent disclosure.

For example, the first time-frequency resources are the last OFDM symbolof the period T1. In the OFDM symbol, all or part of sub-carriers exceptthe sub-carriers occupied by the DM-RS, referring to the second patternshown in FIG. 10, do not need to change the location of the DM-RS.Similarly, if the OFDM symbol contains other reference signals, thefirst time-frequency resources are all or part of sub-carriers exceptthe reference signals.

Compared with the first time-frequency resources described in the firstdefinition mode, the first time-frequency resources described in thesecond definition mode may avoid that other communication nodes occupythe channel to some degree. In the second definition mode, animplementation mode that signals are not sent on the firsttime-frequency resources may be the same as that adopted in the firstdefinition mode.

In a third definition mode, the first time-frequency resources appear inthe period T1 in the time window, and/or appear at a locationimmediately adjacent to the beginning of the time window. The firsttime-frequency resources occupy X OFDM symbols on time dimension, whereX is an integer (for example, X=1) or a fraction. The firsttime-frequency resources may be all sub-carriers on frequency dimension,or all sub-carriers in a predefined bandwidth, or partial predefinedsub-carriers. On these time-frequency resources, the base station sendspredefined signals.

The predefined signals may be distinguished by the same base station, orby base stations of the same operator, or by base stations of the sameoperator in a certain region, or by base stations with the same accesstechnology in a certain region. Accordingly, these base stations maydistinguish other base stations through the predefined signals whenperforming CCA detection, and thus do not regard the predefined signalsof the base stations as interference signals, thereby supportingmultiplexing among these base stations as much as possible.

FIG. 11 is a diagram illustrating first time-frequency resourcesadopting a third definition mode according to an embodiment of thepresent disclosure.

Referring to FIG. 11, the predefined signals may be reference signalscontaining specific identification (ID) information, or may be controlsignals containing specific ID information.

Similarly, if the first time-frequency resources and the DM-RS or RSs ofthe related art that must be sent in the DRS overlap, it is necessary toreset the location of these RSs. If the base station is sending datasignals and reference signals or is sending data signals, the basestation may avoid mapping the data signals and/or reference signals tothe first time-frequency resources through rate matching or puncturing.

At block 102, in a predefined time window, the base station performs atype 2 channel sensing on second time-frequency resources, and decideswhether to send data signals and/or reference signal according to achannel sensing result.

The channel sensing performed by the base station in the predefined timewindow is called the type 1 channel sensing. For example, in atransmission mechanism based on load based equipment (LBE), in animplementation mode (referring to option B in 4.8.3.2 ofen_301893v010800v specification), the maximum transmission time isdetermined by a parameter q, where q is a parameter configured by amanufacturer and meets the requirements on the maximum transmission timein a certain region. The enhanced CCA (eCCA) detection of the channelsensing is determined by a parameter N, where N is not larger than q. Inanother implementation mode, the length of a competition window L isenlarged in a dynamic exponent or multiple relationship according to apredefined rule, or is configured in a semi-static mode. The range ofthe length of the competition window L is [L1, L2] eCCA slots, where L1and L2 may be configured. For example, L1 and L2 need to meetrequirements of a specification. The eCCA detection of the channelsensing is determined by the parameter N, the value of N is [0, L−1].The maximum transmission time may be a predefined value, or may berelative to the value of L1 and/or L2. For example, in Japan, it isspecified that the maximum transmission time is 4 ms. Suppose q=9, thenumber N of CCA slots corresponding to the eCCA detection is a randomnumeral among 0˜q−1, for example, N is equal to 5. Herein, the type 1channel sensing requires that the base station may perform initial CCAdetection in an idle state. The initial CCA detection consists of onesensing interval, e.g., the sensing interval is 34 us or 25 us accordingto the specification. If the initial CCA detection is passed, the basestation may directly send signals. If the initial CCA detection is notpassed, the base station enters an eCCA state. After at least one defer,if there are N=5 idle CCA slots, the base station may send signals. In anon-idle state, the base station only enters the eCCA state.

The channel sensing performed in a predefined time window by the basestation is called the type 2 channel sensing, which enables the basestation to send signals with a shorter delay. The type 2 channel sensingmay be applicable to a scenario that the base station finishes the CCAdetection before the time window and begins to send signals, and/orapplicable to a scenario that the base station does not finish the CCAdetection before the time window but has data signals and DRS to be sentor only has data signals to be sent, and/or applicable to a scenariothat the base station does not finish the CCA detection before the timewindow, but only has the DRS to be sent. The type 2 channel sensing maybe implemented through five implementation modes. For the abovedifferent scenarios, the same implementation mode or differentimplementation modes may be adopted.

The type 2 channel sensing may be implemented through fiveimplementation modes.

In a first implementation mode, the base station performs initial CCAdetection on the second time-frequency resources.

If the initial CCA detection is passed, the base station may directlysend data signals or send data signals and the DRS.

If the initial CCA detection is not passed, the base station performsinitial CCA detection on the next second time-frequency resources.

The second time-frequency resources are a universal set or subset of thefirst time-frequency resources. The second time-frequency resourcesbeing a universal set of the first time-frequency resources means thatthe second time-frequency resources are the same as the firsttime-frequency resources. Referring to FIGS. 2A and 2B, suppose thelength of the first time-frequency resources is one OFDM symbol, thelength of the second time-frequency resources may be smaller than oneOFDM symbol, for example, 34 us. In this embodiment, as the firsttime-frequency resources, the second time-frequency resources may appearperiodically or a-periodically in the time window for a plurality oftimes. The following is described by taking an example that the secondtime-frequency resources appear periodically. In this implementationmode, the period of the first time-frequency resources and the period ofthe second time-frequency resources are the same, but the offset of thefirst time-frequency resources and the offset of the secondtime-frequency resources may be the same or different. The duration ofthe first time-frequency resources is larger than or equal to theduration of the second time-frequency resources.

The second time-frequency resources and the first time-frequencyresources may overlap partially, or do not intersect with each other.

Preferably, for the base station sending data signals in subframes afterthe first time-frequency resources/second time-frequency resources, ifthe base station has passed the initial CCA detection before the end ofthe first time-frequency resources, the base station cannot send anysignal or can only send predefined signals, thereby avoiding hinderingother base stations. The predefined signals are signals that can bedistinguished by other LTE nodes, for example, specific referencesignals. Preferably, if the base station has passed the initial CCAdetection before the end of the first time-frequency resources, the basestation cannot send any signal, and the second time-frequency resourcesare a segment of slots before the next nearest possible sending locationof the DRS, and the length of the second time-frequency resources is thelength of the initial CCA slots. Preferably, if the base station haspassed the initial CCA detection before the end of the firsttime-frequency resources, the base station sends predefined signals, thelength of the second time-frequency resources may not be equal to thelength of the initial CCA slots, and the second time-frequency resourcesmay not be a segment of slots before the next nearest possible sendinglocation of the DRS. For example, the beginning of the secondtime-frequency resources may be the beginning of the firsttime-frequency resources, and the length of the second time-frequencyresources may be the length of one initial CCA slot. Once the initialCCA detection is passed, the base station may send the predefinedsignals until the end of the first time-frequency resources, and beginsto send data signals after the end of the first time-frequencyresources.

For the base station that only sends the DRS in the subframes after thefirst time-frequency resources/the second time-frequency resources, ifthe base station has passed the initial CCA detection before the end ofthe first time-frequency resources/the second time-frequency resources,the base station cannot send any signal or can only send predefinedsignals, thereby avoiding hindering other base stations. Or, as long asthe base station passes the CCA detection, the base station begins tosend signals. The signals may be signals that cannot be distinguished byother base stations.

The following description relates to a scenario that the base stationsends data signals in the subframes after the first time-frequencyresources/the second time-frequency resources, but is not limited to ascenario that the base station only sends the DRS in the subframes afterthe first time-frequency resources/the second time-frequency resources.

In a second implementation mode, the base station performs initial CCAdetection on the second time-frequency resources.

If the initial CCA detection is passed, the base station may directlysend data signals or send data signals and the DRS.

If the initial CCA detection is not passed, the base station enters eCCAby adopting zero defer, or adopting a defer shorter than the type 1channel sensing, or adopting the same defer as the type 1 channelsensing. The number N₁ of idle slots for entering the eCCA by the basestation may be a predefined value or a configured value. The predefinedvalue may be determined according to the maximum consecutivetransmission time of the base station in the time window. For example,if the parameter q is q1 when the maximum consecutive transmission timeof the base station in the time window is 1 ms, and the parameter q isq2 when the maximum consecutive transmission time of the base stationoutside the time window is 4 ms, the eCCA idle slots N1 of the type 2channel sensing is a random integer among 0˜q1−1, i.e., N1∈[0, q1−1],and the eCCA idle slots of the type 1 channel sensing is N∈[0, q2−1]. Itis easy to understand that, since the maximum consecutive occupationtime of the base station in the time window is shortened, the requiredeCCA idle slots are shortened. If the eCCA is passed before the nextsecond time-frequency resources or before the next second time-frequencyresources and possible beginnings of supportable partial subframes, thebase station may send signals on other resources except the firsttime-frequency resources or at the possible beginnings of supportablepartial subframes until the next second time-frequency resources, andperform initial CCA detection on the next second time-frequencyresources. If the eCCA is not passed before the beginning of the nextsecond time-frequency resources, the base station performs initial CCAdetection on the next second time-frequency resources. It should benoted that the length of the maximum competition window of the eCCA maybe unchanged. Before the next second time-frequency resources, the basestation may suspend eCCA counting or continue the eCCA counting. Forexample, the second time-frequency resources may be determined by thepossible beginnings of supportable partial subframes. For example, thepossible beginnings of supportable partial subframes may be the 0^(th),4^(th) and 7^(th) OFDM symbols, and the end of the second time-frequencyresources is the beginning of the 7^(th) OFDM symbol.

FIG. 12 is a diagram illustrating a first implementation mode of type 2channel sensing according to an embodiment of the present disclosure.

FIG. 13 is a diagram illustrating a second implementation mode of type 2channel sensing according to an embodiment of the present disclosure.

The second time-frequency resources and the first time-frequencyresources may overlap partially. Referring to FIG. 13, the secondtime-frequency resources corresponding to the initial CCA detection area subset of the first time-frequency resources. If the initial CCAdetection is failed, the base station enters eCCA, the secondtime-frequency resources corresponding to the eCCA may overlap with thefirst time-frequency resources partially, i.e., the secondtime-frequency resources exceed the first time-frequency resources. Whenthe second time-frequency resources exceed the first time-frequencyresources, as mentioned above, the end of the second time-frequencyresources may be predefined.

It should be noted that, the base station cannot send any signal or canonly send predefined signals on the first time-frequency resources,thereby avoiding hindering other base stations. For example, if the basestation has passed the initial CCA detection or the eCCA detectionbefore the end of the first time-frequency resources, the sendingoperation performed by the base station on the first time-frequencyresources must meet the above requirements.

In a third implementation mode, the base station performs initial CCAdetection on the second time-frequency resources.

If the initial CCA detection is passed, the base station may directlysend data signals or send data signals and the DRS.

FIG. 14 is a diagram illustrating a third implementation mode of type 2channel sensing according to an embodiment of the present disclosure.

If the initial CCA detection is not passed, the base station enters eCCAby adopting zero defer, or adopting a defer shorter than the type 1channel sensing, or adopting the same defer as the type 1 channelsensing. The number N₁ of idle slots for entering the eCCA by the basestation may be a predefined value or a configured value. If the eCCAdetection is passed before the beginning of the next secondtime-frequency resources, the base station may send signals on otherresources except the first time-frequency resources until the nextsecond time-frequency resources, and perform the initial CCA detectionon the next second time-frequency resources. If the eCCA detection isnot passed before the beginning of the next second time-frequencyresources, the base station continues the eCCA detection on the nextsecond time-frequency resources, as shown in FIG. 14.

Similarly, the base station cannot send any signal or can only sendpredefined signals on the first time-frequency resources, therebyavoiding hindering other base stations. For example, if the base stationhas passed the initial CCA detection or the eCCA detection before theend of the first time-frequency resources, the sending operationperformed by the base station on the first time-frequency resources mustmeet the above requirements.

In a fourth implementation mode, the base station performs the initialCCA detection on the second time-frequency resources.

If the base station is in an idle state, the base station performs theinitial CCA detection on the second time-frequency resources accordingto the second or third implementation mode.

If the base station is not in the idle state, the base station performsthe eCCA detection on the second time-frequency resources. The eCCAdetection may be implemented according to the eCCA detection describedin the second or third mode.

In the fourth implementation mode, the type 2 channel sensing has thesame process as the type 1 channel sensing. The difference lies in thatthe number of eCCA idle slots in the type 2 channel sensing is differentfrom that in the type 1 channel sensing, referring to the description inthe second implementation mode.

The difference between the fourth implementation mode and the first,second and third implementation modes lies in that in the fourthimplementation mode, the base station cannot perform the initial CCAdetection unless the base station is in the idle state, which is notlimited in the first, second and third implementation modes.

Similarly, the base station cannot send any signal or can only sendpredefined signals on the first time-frequency resources, therebyavoiding hindering other base stations. For example, if the base stationhas passed the initial CCA detection or the eCCA detection before theend of the first time-frequency resources, the sending operationperformed by the base station on the first time-frequency resources mustmeet the above requirements.

The length of the initial CCA slots in the type 2 channel sensing in theabove four implementation modes may be different from the length of theinitial CCA slots in the type 1 channel sensing, and/or the length ofthe eCCA slots in the above four implementation modes may be differentfrom the length of the eCCA slots in the type 1 channel sensing. Forexample, in order to enable the base station of which data transmissionis interrupted in the DMTC time window to grab a channel as fast aspossible, the length of the initial CCA slots and/or the length of theeCCA slots in the type 2 channel sensing may be shortened. For example,the length of the initial CCA slots in the type 2 channel sensing issmaller than 34 us, and the length of the initial CCA slots in the type1 channel sensing is equal to 34 us. For example, in order to avoid thatthe base station adopting the first implementation mode is much radicalthan WiFi, the length of the initial CCA slots in the type 2 channelsensing may be larger than 34 us, and the length of the initial CCAslots in the type 1 channel sensing may be equal to 34 us.

In a fifth implementation mode, the base station does not perform theinitial CCA detection on the second time-frequency resources, butdirectly send signals. Preferably, the fifth implementation mode isadapted to combine with the second definition mode or the thirddefinition mode of the first time-frequency resources at block 101 ofFIG. 1. In the second definition mode or the third definition mode ofthe first time-frequency resources, the base station does not sendsignals only on part of sub-carriers or send signals on part/allsub-carriers, and the signals of the base station on the firsttime-frequency resources and the second time-frequency resources are notcompletely idle on time dimension. Accordingly, it can be deemed thatthe base station consecutively occupies the channel, and thus a scenariousually does not appear that WiFi grabs the channel on the firsttime-frequency resources.

Preferably, the type 2 channel sensing is applicable to a scenario thatthere are data signals to be sent in the time window. Preferably, thetype 2 channel sensing is applicable to data transmission before thelast first time-frequency resources in the time window.

FIG. 15 is a diagram illustrating type 2 channel sensing in a scenariothat there are data signals to be sent in a DMTC time window accordingto an embodiment of the present disclosure.

For example, referring to FIG. 15, the base station performs the type 2channel sensing on the second time-frequency resources at the end of the1^(th)˜4^(th) subframes in the DMTC time window, and performs the type 1channel sensing at the end of the 5^(th) subframe. There are no firsttime-frequency resources in the 6^(th) subframe, which means that, oncethe base station grabs the channel, the base station may consecutivelysend data signals until general maximum occupation time. That is to say,the data transmission starting from the 6^(th) subframe in the DMTC timewindow is the same as the data transmission outside the DMTC timewindow, and thus the type 1 channel sensing should be adopted.Preferably, the type 2 channel sensing is only applicable to a scenariothat the base station has occupied the channel through the type 1channel sensing and begun to send data signals before the time window.For other scenarios, the type 1 channel sensing is adopted.

FIG. 16 is a diagram illustrating type 2 channel sensing in a scenariothat a channel has been occupied before a DMTC time window to send datasignals according to an embodiment of the present disclosure.

For example, if the base station has occupied the channel and begun tosend data signals before the time window and the channel occupation timedoes not exceed the maximum occupation time, referring to FIG. 16, thetype 2 channel sensing is performed on the second time-frequencyresources at the end of the first subframe in the DMTC time window.After the sending time of the base station reaches the maximumoccupation time, the base station prepares the next transmission. Inthis case, the type 1 channel sensing is adopted. For another example,if the base station performs the type 1 channel sensing before the DMTCtime window, but the value of the eCCA counter does not become 0, andthe CCA detection of the DRS is passed, the base station sends the DRSin the DMTC time window. After sending the DRS, the base stationcontinues the uncompleted type 1 channel sensing. If the eCCA detectionis passed, the base station may send data signals. The process ofcontinuing the uncompleted type 1 channel sensing may include, whensending the DRS, suspending the CCA counter, and after sending the DRS,continuing counting the counter of the type 1 channel sensing. Or, thebase station may count the counter of the type 2 channel sensing aftersending the DRS. That is to say, N may be determined according to themaximum occupation time q1. If the sending time has missed when thevalue of the counter becomes 0, the base station may perform the initialCCA detection on the next second time-frequency resources. Or, if thevalue of the counter does not become 0, the base station may suspend thecounter and continue the CCA detection of the type 2 channel sensing onthe next second time-frequency resources. Similarly, if the base stationonly has data signals rather than the DRS to be sent and performs thetype 1 channel sensing before the DMTC time window, and the value of theeCCA counter does not become 0, the base station may suspend the counterand continue the CCA detection of the type 2 channel sensing on the nextsecond time-frequency resources. Or, the base station may not performthe type 1 channel sensing but perform the type 2 channel sensing in thetime window, for example, adopts the fourth implementation mode of thetype 2 channel sensing.

Preferably, if the base station has occupied the channel through thetype 1 channel sensing and begun to send data signals before the timewindow, the implementation mode X of the type 2 channel sensing isadopted. If the base station has not occupied the channel through thetype 1 channel sensing before the time window, or the base station hasconsecutively occupied the channel for time q2 through theimplementation mode X of the type 2 channel sensing, the implementationmode Y of the type 2 channel sensing is adopted. The implementation modeX may be different from the implementation mode Y.

FIG. 17 is a diagram illustrating type 2 channel sensing performed in aDMTC time window through two modes according to an embodiment of thepresent disclosure.

For example, referring to FIG. 17, if the base station has occupied thechannel through the type 1 channel sensing and begun to send datasignals before the time window, the base station adopts the firstimplementation mode of the type 2 channel sensing. If the base stationhas data to be sent in the DMTC time window or the base station has notoccupied the channel through the type 1 channel sensing before the DMTCtime window, the base station adopts the fourth implementation mode ofthe type 2 channel sensing.

The foregoing is the implementation of the method for channel sensingand signal transmission in the first embodiment.

In the description of the first embodiment and FIG. 1, block 101 isprior to block 102. In actual applications, as mentioned above, forconsecutive subframes of the data signals and/or reference signals inthe time window, the channel sensing may occur before the time window orin the time window. Accordingly, in the time window, the consecutivesubframes of the data signals and/or reference signals may occur beforecertain channel sensing or after certain channel sensing. Or, there maybe only signal transmission but no channel sensing in the time window.Mapping to the blocks in this embodiment, block 101 may be prior toblock 102 or may follow block 102. Or there is only block 101, or thereis only block 102. For example, before the first time-frequencyresources, if the sending node has occupied the channel and begun tosend data signals before the time window and the consecutivetransmission time does not exceed the maximum occupation time, the basestation may not perform channel sensing consecutive transmission in thetime window until the maximum occupation time. For example, suppose themaximum occupation time of unlicensed frequency bands is 4 ms, the basestation has consecutively sent data signals for 3 ms before the DMTCtime window, and the first time-frequency resources appear at the end ofthe first subframe in the DMTC time window. In this case, the basestation does not need to perform channel sensing before the firstsubframe in the DMTC time window, but directly sends data signals. Whensending data signals, the base station does not send signals or sendpredefined signals on the first time-frequency resources. If the basestation has no new data to be sent after this transmission, the basestation may not perform any channel sensing until new data arrive. Inthis case, only block 101 is performed. If the base station has new datato be sent, the base station performs channel sensing in the DMTC timewindow, and does not send signals or send predefined signals on thefirst time-frequency resources. In this case, block 101 is performedfirstly, and then block 102 is performed.

For example, if the base station does not occupy the channel before theDMTC time window and has data to be sent, the base station performschannel sensing in the DMTC time window. If the channel sensing ispassed, the base station may send signals, but does not send signals oronly send predefined signals on the first time-frequency resources. Inthis case, block 102 is performed firstly, and then block 101 isperformed. This embodiment is not limited to the above examples. Whendata signals and/or reference signals are sent for a plurality of timesin the time window, blocks 101 and 102 may be performed alternately. Inthis embodiment and FIG. 1, block 101 is performed before block 102,which is only one of actual applications but is not limited to this casein implementations.

A second embodiment is implemented as follows.

In the second embodiment, when only sending reference signals in thetime window, the sending node performs channel sensing on thirdtime-frequency resources and sends signals after CCA detection isfinished.

FIG. 18 is a flowchart illustrating a method for channel sensing andsignal transmission according to a second embodiment of the presentdisclosure.

Referring to FIG. 18, the method includes following blocks.

At block 1801, before sending reference signals in a predefined timewindow, a base station performs a type 3 channel sensing on the thirdtime-frequency resources. The third time-frequency resources and thefirst time-frequency resources overlap. The base station performs energydetection and/or sequence detection in time domain or in frequencydomain on the third time-frequency resources.

The third time-frequency resources and the first time-frequencyresources overlap, which may be one of following cases.

In a first case, the third time-frequency resources are a subset oruniversal set of the first time-frequency resources.

FIG. 19 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources are a universal set of first time-frequencyresources according to an embodiment of the present disclosure.

Referring to FIG. 19, suppose the third time-frequency resources are theuniversal se of the first time-frequency resources. Suppose base station1 and base station 2 are on the same carrier and may receive signalsfrom each other. Suppose the base station 1 has begun to send databefore the DMTC time window and the base station 2 has no data to besent but needs to send the DRS in the DMTC time window. The base station2 may perform the CCA detection before the beginning of the DMTC timewindow, which is called a type 4 channel sensing to distinguish from theCCA detection performed when sending data signals. In this embodiment,how the base station performs type 4 channel sensing is not limited.This embodiment mainly describes how the type 3 channel sensing isperformed. The type 4 channel sensing may be the same as type 3 channelsensing. If the base station 2 does not pass the type 4 channel sensing,the base station 2 performs the type 3 channel sensing on the thirdtime-frequency resources in the DMTC time window. For example, the lastX OFDM symbol in the end of each subframe in the DMTC time window. Thebase station 2 may send the DRS for once time at the nearest possiblesending location of the DRS if the channel is sensing to be idle for onesensing slot. After sending the DRS, if the base station 2 still has nodata to be sent, the base station 2 may not perform channel sensing.After sending the DRS, if the base station 2 has data to be sent, thebase station 2 may perform the type 1 channel sensing or the type 2channel sensing.

Since the base station 1 does not send any signal or send signals thatcan be recognized by UEs when the base station 2 performs the type 3channel sensing, the base station 1 does not interfere with the channelsensing of the base station 2.

In a second case, the third time-frequency resources are a superset ofthe first time-frequency resources.

FIG. 20 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources is a superset of first time-frequency resourcesaccording to an embodiment of the present disclosure.

Referring to FIG. 20, the third time-frequency resources may be asegment of time-frequency resources before the beginning of eachpossible sending location of the DRS. The third time-frequency resourcescontain the first time-frequency resources. Even, the thirdtime-frequency resources start from the beginning of the DMTC timewindow and contain the entire DMTC time window. The base station 2performs the type 3 channel sensing on the third time-frequencyresources. When there is one idle channel sensing slot, the base station2 may send the DRS for once time at the nearest possible sendinglocation of the DRS. In this way, though the signals sent by the basestation 1 may result in that the base station 2 performs the type 3channel sensing and one or more channel sensing slots may be interfered,it can be ensured that the base station 1 does not interfere with thechannel sensing of the base station 2 in the channel sensing slotscorresponding to the first time-frequency resources.

FIG. 21 is a diagram illustrating type 3 channel sensing when thirdtime-frequency resources and first time-frequency resources intersectpartially according to an embodiment of the present disclosure.

Referring to FIG. 21, in a third case, the third time-frequencyresources and the first time-frequency resources overlap partially.Similarly, though the signals sent by the base station 1 may result inthat the base station 2 performs the type 3 channel sensing and one ormore channel sensing slots may be interfered, it can be ensured that thebase station 1 does not interfere with the channel sensing of the basestation 2 in the channel sensing slots corresponding to the firsttime-frequency resources.

Preferably, if the first definition mode of the first time-frequencyresources in the first embodiment is adopted, the base station mayperform energy detection in time domain on the third time-frequencyresources.

Preferably, if the second definition mode of the first time-frequencyresources in the first embodiment is adopted, the base station mayperform energy detection in time domain on the third time-frequencyresources.

Preferably, if the third definition mode of the first time-frequencyresources in the first embodiment is adopted, the base station mayperform sequence detection in time domain or frequency domain on thethird time-frequency resources. The sequence detection refers to thatthe base station tries to detect a possible sequence, and determine athreshold of the channel sensing, for example, set different thresholdsaccording to whether a sequence is detected, or compare with thethreshold after subtracting the energy of the detected sequence.

At block 1802, if the type 3 channel sensing is passed, that is, if thepower detected by the base station is less than a predefined threshold,the base station may send the DRS; otherwise, the base station performsthe type 3 channel sensing on the third time-frequency resources again.

Preferably, if the base station passes the type 3 channel sensing on thefirst time-frequency resources or the second time-frequency resources,the base station does not send any signal or only sends distinguishablesignals according to the definition mode of the first time-frequencyresources (that is, according to the signal processing mode adopted whenonly the reference signals are sent at block 101 in the firstembodiment) until the nearest possible sending location of the DRS, andsends the DRS.

Preferably, if the base station passes the type 3 channel sensing on thefirst time-frequency resources or the second time-frequency resources,the base station may send reservation signals until the nearest possiblesending location of the DRS, and sends the DRS.

As can be seen from the implementation of the method for channel sensingand signal transmission provided by the present disclosure, becausesignals are not sent or only predefined signals are sent on somereserved resources, channel sensing resources for sending referencesignals may be reserved for other sending nodes, thereby avoiding that asending nodes of the same system hinders another sending node from usingunlicensed frequency bands, improving the frequency domain multiplexingcoefficient among nodes adopting the same access technology, andensuring the coexistence of the access technology and others. Further,through setting the type 2 channel sensing on the second time frequencydomain resources, the length of LBT may be shortened when the referencesignals are sent, thereby rapidly sending the reference signals. Inaddition, through setting the type 3 channel sensing on the thirdtime-frequency resources, the interference with the channel sensing bydifferent base stations of the LAA system can be avoided.

The present disclosure also provides an equipment for channel sensingand signal transmission, which may be applied to the above method. Theequipment includes a channel sensing unit and a signal sending unit. Thechannel sensing unit may be at least one of a processor and a receiver.The signal sending unit may be a transmitter.

The channel sensing unit may perform channel sensing before sending datasignals and/or reference signals, and determine how to perform channelsensing and whether to send the data signals and/or the referencesignals according to a channel sensing result. The signal sending unitmay send signals when the channel sensing unit determines to send thedata signals and/or the reference signals, and when sending the datasignals and/or the reference signals in a predefined time window, doesnot send any signal or send predefined signals on first time-frequencyresources.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a base station in acommunication system, the method comprising: determining whether totransmit a discovery signal not including a physical downlink sharedchannel (PDSCH) or to transmit the PDSCH; in case that it is determinedto transmit the the discovery signal not including the PDSCH,identifying whether an unlicensed frequency band channel is idle for afirst channel sensing interval, and in case that the unlicensedfrequency band channel is idle for the first channel sensing interval,transmitting the discovery signal not including the PDSCH on a firstperiod; and in case that it is determined to transmit the PDSCH,identifying whether the unlicensed frequency band channel is idle for asecond channel sensing interval, and in case that the unlicensedfrequency band channel is idle for the second channel sensing interval,transmitting the PDSCH on a second period, wherein a duration of thefirst channel sensing interval is equal to or shorter than a duration ofthe second channel sensing interval.
 2. The method of claim 1, whereinthe discovery signal not including the PDSCH is transmitted on the firstperiod in a subframe within a predetermined timing window when aduration of the first period is less than 1 ms.
 3. The method of claim2, wherein a duration of the subframe corresponds to a duration of 14orthogonal frequency division multiplexing (OFDM) symbols, and wherein aduration of the first period corresponds to 12 OFDM symbols of the 14OFDM symbols within the subframe.
 4. The method of claim 2, wherein thepredetermined timing window is a timing window for radio resourcemanagement (RRM) measurement.
 5. The method of claim 2, wherein thepredetermined timing window is a discovery signals (DRS) measurementtiming configuration (DMTC) window.
 6. The method of claim 1, wherein aduration of the first period is shorter than a duration of the secondperiod.
 7. The method of claim 1, wherein a starting symbol and a lastsymbol of the first period in a subframe are a first cell specificreference signal (CRS) symbol and a second CRS symbol in the subframe,respectively.
 8. The method of claim 1, wherein the duration of thefirst channel sensing interval includes 25 μs.
 9. A base station in acommunication system, the base station comprising: a transceiver; and acontroller coupled with the transceiver and configured to: determinewhether to transmit a discovery signal not including a physical downlinkshared channel (PDSCH) or to transmit the PDSCH, in case that it isdetermined to transmit the discovery signal not including the PDSCH,identify whether an unlicensed frequency band channel is idle for afirst channel sensing interval, and in case that the unlicensedfrequency band channel is idle for the first channel sensing interval,transmit the discovery signal not including the PDSCH on a first period,and in case that it is determined to transmit the PDSCH, identifywhether the unlicensed frequency band channel is idle for a secondchannel sensing interval, and in case that the unlicensed frequency bandchannel is idle for the second channel sensing interval, transmit thePDSCH on a second period, wherein a duration of the first channelsensing interval is equal to or shorter than a duration of the secondchannel sensing interval.
 10. The base station of claim 9, wherein thediscovery signal not including the PDSCH is transmitted on the firstperiod in a subframe within a predetermined timing window when aduration of the first period is less than 1 ms.
 11. The base station ofclaim 10, wherein a duration of the subframe corresponds to a durationof 14 orthogonal frequency division multiplexing (OFDM) symbols, andwherein a duration of the first period corresponds to 12 OFDM symbols ofthe 14 OFDM symbols within the subframe.
 12. The base station of claim10, wherein the predetermined timing window is a timing window for radioresource management (RRM) measurement.
 13. The base station of claim 10,wherein the predetermined timing window is a discovery signals (DRS)measurement timing configuration (DMTC) window.
 14. The base station ofclaim 9, wherein a duration of the first period is shorter than aduration of the second period.
 15. The base station of claim 9, whereina starting symbol and a last symbol of the first period in a subframeare a first cell specific reference signal (CRS) symbol and a second CRSsymbol in the subframe, respectively.
 16. The base station of claim 9,wherein the first channel sensing interval includes 25 μs.